Net::SSH::Perl::SubsysUser:Contributed PerNet::SSH::Perl::Subsystem::Server(3)NAMENet::SSH::Perl::Subsystem::Server - Server infrastructure for SSH
subsystems
SYNOPSIS
use Net::SSH::Perl::Subsystem::Server;
use base qw( Net::SSH::Perl::Subsystem::Server );
use constant MSG_FOO => 1;
sub init {
my $ss = shift;
$ss->SUPER::init(@_);
$ss->register_handler(MSG_FOO, \&handle_foo);
}
sub handle_foo {
my $ss = shift;
my($msg) = @_;
print "Got MSG_FOO message!\n";
}
DESCRIPTIONNet::SSH::Perl::Subsystem::Server is a generic subclass that can be
used to build servers for SSH-2 subsystems. A subsystem is a network
protocol that runs on top of a secure, encrypted SSH connection between
two machines: it allows the user and developer to build a secure
network protocol without worrying about the details of that security,
because it inherits the secure tunnel from SSH.
Subsystem::Server provides basic functionality needed by all subsystem
servers. A subsystem daemon is started up by the sshd when a request
comes in for that subsystem; sshd and the subsystem daemon then talk to
each other through pipes, and data that the daemon wishes to send to
the subsystem client is sent over the network through the SSH secure
tunnel. Subsystem::Server handles the talking to the sshd, and lets the
application developer focus on designing the network protocol and
handling requests from the subsystem client.
USAGENet::SSH::Perl::Subsystem::Server is meant to be used as a base class
for subsystem servers. With that in mind, general usage should follow
the example above in the SYNOPSIS:
· Initialization
If you want your subclass to do anything, you'll want to override
the init method so that you can set up handlers for specific types
of messages from the subsystem client. For each message type, you
need to associate the type with a subroutine reference that will be
invoked when a message of that type is received by the core server.
You do this by calling the register_handler method (see below).
· Message Handling
When the core server receives new messages from the client, it
grabs the first byte from the incoming stream; the first byte is a
packed 8-bit integer representing the type of the message. This
identifier is used to look up the message handler to handle this
particular type of message.
These are the public methods in which your subclass will be most
interested:
$ss->init(%args)
Initializes the subsystem server object. This is where you'll want to
set up your message handlers (using register_handler) and perhaps
perform any other protocol-specific initialization.
Make sure that your init method returns the $ss object on success;
failure to return init should be an indication of failure to calling
code.
%args can contain whatever you like it to contain. The base class
Net::SSH::Perl::Subsystem::Server takes these parameters in %args:
· Log
The location of a file on disk where you can write messages to be
logged. This is the file to which messages sent to the log method
(below) will be written.
This is an optional argument; if not specified, no log file will be
used, and calls to log will be silently ignored.
$ss->register_handler($type, $code)
Configures the subsystem server $ss such that any message sent from the
client whose type is $type will automatically invoke the subroutine
reference $code. This is how you build protocol-specific functionality
into your subsystem: you associate message types with methods.
The subroutine reference $code will be invoked and given two arguments:
$ss, the instance of the subsystem server that is blessed into your
subclass, and $msg, a buffer in the class Net::SSH::Perl::Buffer
(although you can choose a different buffer class--see buffer_class,
below).
$ss->send_msg($msg)
Sends the message $msg to the client. Or, in more technical terms, adds
the message $msg to the server's output queue, to be written back to
the client the next time through the select loop.
$msg should be a buffer in the class Net::SSH::Perl::Buffer (although
you can choose a different buffer class--see buffer_class, below).
$ss->serve
Enters the select loop, waiting for requests from the client. Users of
your class should call this method when they're ready to start serving
clients.
$ss->log($message)
Writes the log message $message to the log file, if one was specified
as the Log argument to init (or, rather, to the constructor).
If a log file was not specified, returns silently.
$ss->buffer_class
By default, messages are represented by Net::SSH::Perl::Buffer objects.
You can alter this by overriding the buffer_class method; it should
return the name of an alternate class. Be aware that this alternate
class must conform to the interface used by Net::SSH::Perl::Buffer, so
you may be best off subclassing that class and adding in your own
functionality.
NOTES
It should be noted that the external interface (API) to this module is
alpha, and could change.
AUTHOR & COPYRIGHTS
Please see the Net::SSH::Perl manpage for author, copyright, and
license information.
perl v5.14.12008-10-Net::SSH::Perl::Subsystem::Server(3)
